There are many instances in the prior art in which a coating must be applied to a continuously moving web or film. In the prior art coatings solutions generally include a solvent which facilitates the application of the coating to the web.
One of the problems which exists in coating systems of the prior art is pollution resulting from the evaporation of the solvent after the coating has been applied. Very expensive installations such as an incinerator or solvent recovery systems are required in order to obviate the harmful effects of such pollution.
In order to overcome the problem desccribed above, it has been suggested that water be substituted for the solvents normally employed. Application of such a material, however, is still difficult owing to the low viscosity of the material.
One modern coating system which has been proposed is one which uses no solvent but which is applied in liquid form and immediately cured. A system of this type is known as a 100% solids system. While such a system successfully avoids the problem of pollution, it is, as will be appreciated, extremely difficult to apply a thin coating since there is no evaporation. That is to say, where the material being applied includes a solvent which evaporates after application, a relatively thick coating can be applied to leave the desired thin coating when the solvent evaporates. However, where a 100% solids material is being applied, the initial coating of material must be very nearly the same thickness as the desired coating.
Various forms of coating apparatus are known in the prior art. Most of these systems include resilient lips or blades which are designed to control the thickness of the applied layer. Such apparatus has not been successfully employed to apply a thin coating in a 100% solids coating system.